Oxidation of propionaldehyde in aged boric-acid-coated vessels. Part 1.—Kinetic results

Abstract

The maximum rate of oxidation of propionaldehyde in aged boric-acid-coated vessels at 440°C has orders of 1.5 and 0.2 with respect to aldehyde and oxygen respectively. The rate is independent of vessel diameter and is accelerated by addition of inert gas. The main kinetic features can be accounted for by a mechanism in which the rate-determining steps are: C₂H₅CHO + O₂= C₂H₅CO + HO₂(1), HO₂+ C₂H₅CHO = H₂O₂+ C₂H₅CO (4), 2HO₂= H₂O₂+ O₂(5), H₂O₂+ M′= 2OH + M′(7)

The autocatalytic nature of the reaction is attributed to reaction (7), which also accounts for the accelerating effect of inert gas. Solution of the simultaneous differential equations for –d[C₂H₅CHO]/dt and d[H₂O₂]/dt gives the value of k₁= 0.076 ± 0.020 l. mole^–1 sec^–1, and the values of k₄/k^½₅= 39 ± 5 (l. mole^–1 sec^–1)^½. Using k₅= 1.8 × 10⁹ gives k₄= 1.85 × 10⁶ l. mole^–1 sec^–1 at 440°C.